Document --from-gron

Author: IvanIsCoding

docs/manual.md

@@ -150,6 +150,7 @@ This file contains the simplified response from the Yahoo Finance Unofficial JSO
   * [Pretty Printing](#pretty-printing)
   * [Raw Output](#raw-output)
   * [Grep friendly output](#grep-friendly-output)
+  * [Reverting filtered grep output](#reverting-filtered-grep-output)
 
 ### Reading Files
 
@@ -475,6 +476,40 @@ json.bin[0].path = "src/main.rs";
 
 If you need deterministic outputs, we recommend using the `-S` flag for sorting the output.
 
+### Reverting filtered grep output
+
+`celq` also has a `--from-gron` flag that parsers the output of `gron` and `celq --greppable`. It is equivalent to `gron -u`. That can be useful for converting output filtered by grep back to JSON.
+
+For example:
+
+```bash
+celq -g 'this' < yfinance.json | rg '\bregularMarket\w*' | celq --from-gron -S -p 'this'
+```
+
+Outputs:
+
+<details>
+<summary>ripgrep output back to JSON</summary>
+
+```json
+{
+  "chart": {
+    "result": [
+      {
+        "meta": {
+          "regularMarketDayHigh": 277.825,
+          "regularMarketDayLow": 269.02,
+          "regularMarketPrice": 271.01,
+          "regularMarketTime": 1767387600
+        }
+      }
+    ]
+  }
+}
+```
+
+</details>
+
 ## Quirks
 
 1. Do not rely on the order of the JSON output, by default it is randomized due to Rust implementation details. If you need ordering, pass `--sort-keys` as an argument

src/ungron.rs

@@ -32,8 +32,6 @@ fn parse_and_apply_line(line: &str, root: &mut JsonValue) -> Result<()> {
         set_value_at_path(root, &path, value)?;
         Ok(())
     } else {
-        // gron occasionally emits 'const' or 'var' depending on flags,
-        // but standard gron is pure assignment.
         Err(anyhow!("Expected assignment (e.g., json.a = 1)"))
     }
 }
@@ -139,7 +137,7 @@ fn set_value_at_path(root: &mut JsonValue, path: &[PathSegment], value: JsonValu
         }
     }
 
-    // Logic Fix: Don't overwrite an existing object/array with an empty one.
+    // Don't overwrite an existing object/array with an empty one.
     if (value.is_object() && value.as_object().unwrap().is_empty() && cur.is_object())
         || (value.is_array() && value.as_array().unwrap().is_empty() && cur.is_array())
     {